Process for the manufacture of tipless incandescent lamps



April 13 1926. 1.5805226 G. F. WEBB PROCESS FOR THE MANUFACTURE OF TIPLESS INCANDESCENT LAMPS Filed Oct. 17 1925 E|cr6 era/e6; f. 1/555 grwenioz .Patented Apr. 13, 1926. 1

1,580,226 PATENT OFFICE.

GEORGE F. WEBB, 0F HAMILTON, ONTARIO, CANADA.

PROCESS FOR THE MANUFACTURE OF TIPLESS INCANDESCENT LAMPS.

Application filed October 17, 1925. Serial No. 63,053.

To all whom it may concern:

Be it known that GEORGE F. WEBB, a subject of the King of Great Britain, re-

siding at Hamilton, in the county of Went worth and Province of Ontario, Canada, has invented certain new and useful Improvements in a Process for the Manufacture of Tipless Incandescent Lamps, of whichthe following is a specification.

This invention. relates to improvements -in the process of manufacturing tipless incandescent lamp bulbs. This class of electric light bulb has become well known in the art and is very popular with the trade on account of the absence .of the familiar tip on the exposed end of the blub which formerly cast an undesirable shadow, orspot, as it was sometimes called, and which was objectionably dangerous by reason of the sharply pointed nature of this tip. But these tipless lamp bulbs have been very expensive to manufacture on account of the difficult and lengthyprocess of manufacture, and the high degree of waste caused by imperfection arising out of inefficient manufacturing methods.

Various different processes have effectively been employed to unite an exhaust tube with the leading-in tube, but most of these processes have involved an additional fusing operation, or, if practised simultane-- ously with the coalescence of the stem and leading-in tube, the operation is very delicate and requiring of highly skilled workmanship.

This invention relates particularly to the forming of the stem body by uniting the filament stem, leading-in tube and exhaust tube at one heating or fusing.

With the exclusion of that process consisting of uniting the exhaust tube tothe leading-in tube by fusing these two members together in adistinctly separate and additional operation; broadly speaking, there are two prior methods open by which the exhaust tube can be'united with the leading-in tube during'the period the glass is plastic while the filament carrying stem, leading-in tube and lead wires are assembled. The first of these methods comprises principally the application of air pressure to form a passage through the massed plastic glass forming the usual union of the filament carrying stem and the leading-in tube and in which the lead wires are confined. This method results in a high degree The second of these methods consists essentially of uniting the exhaust tube to the leading-in tube just above the mass formed by the union of the filament carrying stem and leading-in tube and while the mass and adjoining glass is plastic and hot, the external or opposite end of the exhaust tube being sealed so that the air within it expands under the heat to force an opening at the point of union.

This latter method is considerably preferable to the former, particularly for the reason that the union of the exhaust tube with the leading-in tube is distinctly separate from the said mass although made simultaneously therewith, but sometimes it is preferable to blow out the opening at the point of union by applied air pressure, that is, air pressure applied to an open ended exhaust tube.

Therefore, the principal object of this invention' is to provide means for substantially simplifying and reducing the heating steps in the process of uniting an exhaust tube to a leading-in tube at a point distinctly separate from the mass formed by uniting the filament stem with the leading-in tube, and blowing out an opening in the leadingin tube to communicate with an end of the exhaust tube by means of an air current applied near the opposite end of the latter tube.

A second important object is to provide a process which will enable unskilled operators to construct and assemble the stem bodies of tipless incandescent lamps in accordance with this invention, so that any waste or imperfection occurring will result only from inexcusable carelessness on the part of such operators.

A third. important object is to provide a process of the class specified embodying the application of air pressure to the free end of the exhaust tube for the purpose of blowing out the communication opening referred to herein, where the pressure of the air is immaterial beyond a certain minimum degree, and where such air pressure may be applied as a momentary introduction of an air current and not necessarily established by a closed communication with an air pressure SOHI'CB.

A fourth important object is to create a substantial conservation of exhaust tubing in the manufacture of these lamps, as ex haust tubes of considerably less length may be employed in the execution of this process than in the prior art.

These, together with other objects may be attained in the manner which will be hereinafter more fully described, illustrated in the accompanying drawing, and specificall pointed out in the claim hereunto appende Figure 1 is an elevation of an exhaust tube and filament carrying stem;

Figure 2 is a sectional elevation of the leading-in tube, exhaust tube, filament carrying stem and lead wires in position as in preparation for coalescence by application of heat;

Figure 3 is a sectional elevation of the stem body, including the mass, comprised of the units characterized in the description of Figure 2 subsequent to the consummation of coalescence;

Figure 4 is a sectional elevation of the structure shown in Figure 3 as seen when given a quarter turn on its axis;

Figure 5 is a sectional elevation of the structure shown in Figure 4: assembled to the incandescent lamp bulb; and,

Figure 6 is a sectional elevation of the completed glass parts of the lamp.

Similar reference characters refer to similar parts throughout the several views.

The filament carrying stem is indicated on the drawing by the numeral 10, and the exhaust tube which is straight throughout its length and open at each end is indicated by the numeral 11. The leading-in tube comprises a cylinder 12 open at both ends and having the usual flare 13 at the outer end to the periphery of which is later welded the neck of the lamp bulb 14. The stem 10 is concentrically aligned with the lead ing-in tube 12 and enters this tube so far as it is to be coalesced by fusion. The exhaust tube 11 is inserted through the opposite or flared end of the leading-in tube and axially aligned with the stem 10 with an intervening space between their ends. The lead wires 15 are also positioned. Heat is now applied to the lower end of the leading-in tube and thus coalescence takes place between this end of the leading-in tube and the end of the stem 10 by fusion, thusclosing the end of the leading-in tube. This' forms a mass 16 and while this mass is yet semi-molten or plastic a clamping device compresses it to a solid fiat state. During this fusion and coalescence of the stem and leading-in tube and forming of the mass 16, the proximal glass of the leading-in tube and the inner end of the exhaust tube becomes plastic, and the heat attracts the end of the exhaust tube toward the wall of the leading-in tube, the former being thus welded to thelatter. Justas this welding takes place, a current of gas or air is introduced into the exhaust tube from its outer end, and-the current of air thus introduced blows out the film of plastic glass closing the welded end of said tube, thus establishing communication from the outside of the leading-in'tube to the inside .of the exhaust tube as indicated at 17. In

this manner the exhaust tube is assembled to the stem body during the same operation as 1:hat of uniting the stem to the leading-in tn 6.

After the stem body has been secured to the neck of the lamp bulb as shown in Figure 5, the air Within the lamp bulb is exhausted through the exhaust tube 11, after which the exhausttube is fused to a mass formation which seals it as near as practicable to the flare 13 as indicated by 19,

and the remaining end is then broken away or-severed by fusing clean through and discarded.

' There has thus been produced a simple and efficient process of the class described and for the purpose specified.

Having now fully disclosed my invention and how it is tobe performed and ascertained, what I claim, is

The method of uniting the exhaust tube with the leading-in tube of tipless incandescent lamps during the process of uniting the filament carrying stem with the leading-in tube, which consists of axially aligning the filament carrying stem and exhaust tube with their nearest ends within the leading-in tube and with a substantial intervening space between such ends, fusing to plasticity and producing massed ccalcfcence of the end of the filament carrying stem and the proximal portion of the leading-in tube, thereby causing the end of the exhaust tube to bend toward the wall of .the leading-in tube by heat attraction and become welded to said wall adjacent the mass formed aforesaid, introducing an air current into the exhaust tube from its outer end while the union of the exhaust tube with the leading-in tube is yet plastic thereby blowing an opening in the latter tube at the end of the former tube whereby communication is established from outside the leading-in tube to the inside of the exhaust tube.

In testimony whereof I have afiixed my signature.

GEORGE E. WEBB. 

